Females: Distal segments and terminal chaetae of right and left P5 asymmetrical, projection curved to be nearly parallel to the long axis of the segment, contains fewer than 8 teeth.
Sea of Japan, Arctic coast of Alaska, Bering Sea, Chukchi Sea, Sea of Okhotsk
Coastal species, characteristic for brackish waters. In regions of fresh water influence may be found in very large numbers, along with Eurytemora herdmani.
Females: Three non-fused thoracic segments, the back corners of the last thoracic segment carry wing-like growths (characteristic for the genus), which reach almost to the end of the genital segment. After Heron (1964, p.209) specimens of adult females varied considerably in the development of metasomal wings. Specimens withoiut wings appeared with left metasomal lobe slightly larger. Rostrum bifurcate with 2 small filaments. Abdomen contains 3 segments. Genital segment widens in the sides, is as long as either of the next 2 segments. Caudal rami relatively short for the genus, not longer than the third abdominal segment. Abdomen carries weak armature: the genital segment and second abdominal segment carry 2 short chaetae on each side on each segment, the third segment carries 1 chaeta on each side. Caudal rami lacks armature, only the inner side carries a row of chaetae. P5 assymetrical, monoramous, each branch is composed of 3 segments. The first segment carries 2 spines on the outer side and on the inner side a sharp projection covered with small spines. The distal segment is armed with one lateral and one long apical spine. Asymmetry is evident in the length of the distal segment and the inner projection - they are both longer on the right branch. However, the apical spine is much larger on the left branch.
Males: The back corners of the last thoracic segment are rounded, body more slender than in females. A1 geniculate. Abdomen contains 5 segments, the caudal rami are equal in length to the last 2 segments combined. P5 assymetrical, monoramous, each branch is composed of 4 segments (boundaries between segments may not be very clear). The distal segment is elongated and curved on the right branch, and angular and wider than the base of the third segment on the left branch.
Egg-brooding species
Females: 0.99-1.29 mm
Males: 0.92-1.16 mm
